A case of a pleomorphic hyalinizing angiectatic tumor of soft parts with intracytoplasmic hemosiderin pigment apparent upon fine-needle aspiration cytology.

Pleomorphic hyalinizing angiectatic tumors of soft parts are extremely rare low-grade mesenchymal lesions that frequently occur subcutaneously, especially in the lower extremity. The tumor is histologically characterized by sheets of plump, spindled or rounded cells, and clusters of ectatic blood vessels. It also has a number of previously characterized cytological features such as pleomorphic cells, intranuclear pseudoinclusion, and intracytoplasmic hemosiderin pigments. However, intracytoplasmic hemosiderin has not been carefully evaluated in cytology specimens. Here, we report the case of a 56-year-old Japanese man with an encapsulated pleomorphic hyalinizing angiectatic tumor of soft parts that included fine and coarse hemosiderin-laden tumor cells. The tumor was clinically followed up as a hematoma, but malignant tumors, including malignant melanoma, were suspected because aspiration cytology specimens contained pleomorphic cells with intracytoplasmic brown pigments. The tumor was closely associated with an intratumoral hematoma and a few microscopic satellite lesions. Pleomorphic hyalinizing angiectatic tumor of soft parts should be included in the differential cytological diagnosis of soft tissue tumors if the three cytological features described earlier are present. Enucleation therapy could facilitate local recurrence, as the tumor may have the potential to infiltrate surrounding soft tissue or form satellite lesions.